Processes for the manufacturing of paper products for use in tissue, toweling and sanitary products generally involve the preparation of an aqueous slurry of paper fibers and then subsequently removing the water from the slurry while contemporaneously rearranging the fibers in the slurry to form a paper web. Various types of machinery can be employed to assist in the dewatering process.
The processes to manufacture these paper products use a paper slurry that is fed onto the top surface of a traveling endless belt that serves as the initial papermaking surface of the machine. These papermaking belts or fabrics carry various names depending on their intended use. Fourdrinier wires, also known as Fourdrinier belts, forming wires, or forming fabrics are used in the initial forming zone of the papermaking machine. Dryer fabrics carry the paper web through the drying operation of the papermaking machine.
One particular papermaking belt utilizes a foraminous woven member surrounded by a hardened photosensitive resin framework. The resin framework has a plurality of discrete, isolated, channels known as “deflection conduits” disposed therein. The process to manufacture a paper product can involve the steps of associating an embryonic web of papermaking fibers with the top surface of the papermaking belt, deflecting the paper fibers into the deflection conduits, and applying a vacuum or other fluid pressure differential to the web from the backside (machine-contacting side) of the papermaking belt. This process made it finally possible to create paper having certain desired preselected characteristics.
Although the aforementioned process produces suitable papermaking belts and results in superior formed paper products, it has been found that the papermaking manufacturing environment severely limits the lifetime of these papermaking belts. This could be attributed to the inability to measure certain key physical parameters of the papermaking belt during use. By way of example, the equipment used in the manufacture of paper products subjects the papermaking belt to extreme temperatures, bending moments, tensions, stress, strain, pH, wear, and the like. Each of these factors has been found to severely limit the life of the papermaking belts by causing micro-fractures to occur in the hardened resins that form the surface of the papermaking belt as well as fractures due to oxidation and decay of the resin itself. Without desiring to be bound by theory, resin loss is believed to be the primary cause of belt failure. This is particularly true of papermaking systems that incorporate the use of high temperature pre-dryers and Yankee drying drums. Additionally, the high pressures experienced by the papermaking belt in process nips (formed between pressure rolls) and vacuum slots, as well as process abrasion points (e.g., while traversing vacuum boxes and the like) and stresses introduced by misaligned process equipment have been linked to premature papermaking belt failures.
The significance of the difficulties experienced by users of these papermaking belts is exacerbatingly increased by the relatively high cost of the papermaking belts themselves. For example, manufacturing a foraminous woven element that is incorporated into these belts requires expensive textile processing operations, including the use of large and costly looms. Also, substantial quantities of relatively expensive filaments are incorporated into these foraminous woven elements. The cost of these papermaking belts is further increased when filaments having high heat resistance properties are used. These special filaments are generally necessary for papermaking belts that pass through various high temperature drying operations.
In addition to the cost of the belt itself, the decay and/or failure of a papermaking belt can also have serious implications on the efficiency of the papermaking process and the paper products so produced. A high frequency of paper machine belt failures can substantially affect the economies of a paper manufacturing business due to the loss of the use of the expensive papermaking machinery (that is, the machine “downtime”) during the time a replacement belt is being fitted on the papermaking machine.
Therefore, a need exists for an improved papermaking belt, a method of making a papermaking belt, and an ability to monitor the physical condition of a papermaking belt during use in the production of paper products that can eliminate the foregoing problems. In short, the ability to measure the physical condition of the papermaking belt made by the prior processes during use can provide for real-time in situ feedback into the papermaking process that can stimulate process changes necessary to produce quality paper products and simultaneously increase papermaking belt life.